TMcC:
All good advice above, however I highly recommend the clean slate method.
A reformat and re-installation of Windows can do wonders for your machine. We do it every few years around my house and office.
XP can become damaged and loaded with junk of all kinds that will slow your machine down. One item that begs for help is the registry. This group of files grows with each software installation and there are no easy ways around
thoroughly cleaning it up. Rather than attempting what may end up being a frustrating hunt and peck method, I would say go for it.
Couple of things: Backing up everything on your disk is best if you have the capability.
At the very least, save the contents of your Documents and Settings Folder and subfolders along with the folders you know have your data within.
Specific things you may want to do: Export your Outlook (or Outlook Express) Email and News accounts for easy configuration.
Export your Windows Address book.
Save your favourites.
Save your email folder and re-import.
MS Office templates if you have created custom ones.
MS Outlook (not Express) .pst file if you use this program.
Download and make a CDROM of the latest drivers for: Video
Network Card
Sound Card
USB
Peripherals like printers and scanners.
Details on the manufacturers of the above hardware can be found in your My Computer Properties box.
Look around for your data. Not all programs save your work
in the My Documents folder.
Recall and record your various passwords used on the web. (this one always gives me a headache)
Download and backup an IT professional copy of the Windows XP SP2 (service pack 2) to ease the Windows Update process.
Download and backup the latest version of DirectX.
www.microsoft.com/downloads.
Whatever you decide to do, Good Luck!